Seismic traces are weighted and stacked to produce an estimated output trace having improved signal-to-noise ratio. Those traces having the highest signal-to-noise ratio are weighted more heavily. The weights for each trace are determined from a detection of the signal between the estimated output trace and each of the seismic traces. The procedure is iterated so that the signal-to-noise ratio of the estimated output trace is progressively improved by recomputing the weights of the individual traces on each pass.